Exercise May Be Worth the Risk in Kids with Hemophilia

Action Points

Explain that an Australian study found an increase in bleeding risk associated with vigorous physical activity in hemophiliacs but a link to only one more bleeding episode per year with weekly sports participation, suggesting an overall low absolute increase in risk.

Note that there was a strong association between calculated clotting factor level and bleeding risk.

Children who have hemophilia are at increased risk for bleeding episodes if they participate in vigorous physical activity, but the risk is modest and may not outweigh the potential benefits of exercise, Australian researchers suggested.

The odds ratios for a bleed were 2.7 (95% CI 1.7 to 4.8, P<0.001) for a boy playing a sport with some contact such as basketball and 3.7 (95% CI 2.3 to 7.3, P<0.001) for a high-contact sport such as wrestling, according to Carolyn R. Broderick, MBBS, of the University of Sydney, and colleagues.

Those odds ratios suggest that "for most children, the absolute increase in risk associated with physical activity is low," the researchers observed in the Oct. 10 issue of the Journal of the American Medical Association.

Moreover, for a child who typically experiences five bleeding episodes during a 1-year period, only one of the bleeds would be expected to result from weekly participation in those activities, they calculated.

Before the introduction of prophylactic clotting factors, children with hemophilia were discouraged from participating in vigorous sports because of the likelihood of bleeding into joints.

However, that caution may no longer be needed with the availability of effective treatments, the researchers suggested.

In an editorial accompanying the study, Marilyn J. Manco-Johnson, MD, of the University of Colorado in Aurora noted that participation in sports can be psychologically very helpful for young patients.

"Participation in a popular sport can be important to reduce the sense of isolation experienced by many boys with hemophilia," she wrote.

With the goal of quantifying the risks associated with exercise so that patients and caregivers can make informed decisions about participation, Broderick's group enrolled 104 boys with moderate or severe hemophilia A or B, following them for a year.

In a study with a case-crossover design in which patients served as their own controls, patients or parents were asked to contact the researchers in the event of a bleed, at which time they were interviewed about recent activities.

The 8-hour period immediately preceding the onset of symptoms was considered the window of interest, while the corresponding time periods in the 2 days before the event represented control periods.

Physical activities with no expected collisions between participants such as swimming were classified as category 1.

Category 2 activities such as basketball were those with the possibility of rough contact between players, while category 3 were those such as wrestling with certain contact.

Clotting factor levels, a potential confounder, were estimated and adjusted for using a pharmacokinetic model.

Mean age of the study participants was 9.5, and more than 80% had hemophilia A and severe involvement as determined by blood levels of clotting factor.

A total of 86% were on a regular prophylactic schedule of clotting factor.

During 1 year of follow-up, patients with moderate disease had a median of five episodes, while those classified as severe had three.

A total of 336 bleeds were included in the analysis, with the knee, ankle, and elbow being the most common sites.

During 31% of the bleed windows of interest there had been participation in a category 2 activity, as there had been during 25% and 21% of the first and second control windows.

During 7% of the bleed windows there had been a category 3 activity, as there had been in 3% and 5% of the two control windows.

The odds ratio for the blood level of clotting factor was 0.980 (95% CI 0.965 to 0.992), which meant that for every 1% increase in the level of clotting factor, the incidence rate was decreased by 2%, the researchers explained.

That ratio then was used to calculate the amount of clotting factor that would be needed for risk reduction, which was estimated at 22 IU/kg of factor VIII to cut the bleeding risk by half.

In addition, physical activity was more likely during the hour before the bleed, which suggested that timing of prophylactic infusions of clotting factor could be adjusted according to sports participation, according to Manco-Johnson.

In her editorial, she observed that the finding that participation in contact sports did not worsen hemophilia outcomes "may seem counterintuitive and inconsistent with conventional wisdom."

"However, the study by Broderick et al. suggests that a factor level below a critical threshold is a more important determinant of bleeding risk than modest exposure to vigorous activity," she wrote.

Guidelines on sports participation for children with hemophilia are needed, she argued.

"These recommendations should include educating parents and athletes about potential short and long complications related to sports participation, risk reduction measures with prophylaxis regimens, conditioning and strengthening programs, and the healthful contributions of sports participation toward physical, social, and emotional development as well as the prevention of obesity," she stated.

Limitations of the study included the possibility of recall bias, patients' self-report of bleeding events, and a lack of information on subclinical bleeds.

The study was funded by the Australian National Health and Medical Research Council and the Australian Research Council.

Several of the authors have received competitive research grants from the Bayer Hemophilia Awards Program, as well as fees and grants from Novo Nordisk, Bayer, Baxter Health Care, Pfizer, and CSL-Behring.